Data and Voice separation with 802.11n

Answered Question
Apr 21st, 2009

Hi there

I'm interessting in some design guides. I would deploy data in 2.4 GHz band and the voice in 5 GHz band. But aren't there problems with the 802.11n deployment, I thought that this works better in 5 GHz.

What recommendations would you make and did you have some issues with this design?

Thanks in advance.

Dominic

I have this problem too.
0 votes
Correct Answer by jeff.kish about 7 years 7 months ago

Hi Dominic,

You can find all kinds of documentation on Cisco's 802.11n homepage: http://www.cisco.com/en/US/netsol/ns767/networking_solutions_package.html

To answer your questions, there is no "problem" with running 802.11n in the 2.4GHz space, but there are limitations. You cannot use channel-bonding, which is the primary source of the added bandwidth that 802.11n offers. If you want to see 150Mbps data rates, you'll need to deploy it in a 5GHz implementation.

Another advantage to running in 5GHz is that you can isolate your 802.11n traffic from your 802.11b/g traffic on the 2.4GHz radio. This will prevent slowdown that can occur when legacy clients coexist with 802.11n clients.

So yes, you're correct to say that it does work better in 5GHz. The nice thing is that most 802.11n chips in laptops support this band.

That said, it would be best if voice and data can both exist in the 5GHz space. You can accomplish this by creating different SSIDs for your voice and data networks. There is nothing wrong with deploying both in 5GHz.

Let me know if you have anymore questions. Thanks!

Jeff

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Correct Answer
jeff.kish Tue, 04/21/2009 - 08:28

Hi Dominic,

You can find all kinds of documentation on Cisco's 802.11n homepage: http://www.cisco.com/en/US/netsol/ns767/networking_solutions_package.html

To answer your questions, there is no "problem" with running 802.11n in the 2.4GHz space, but there are limitations. You cannot use channel-bonding, which is the primary source of the added bandwidth that 802.11n offers. If you want to see 150Mbps data rates, you'll need to deploy it in a 5GHz implementation.

Another advantage to running in 5GHz is that you can isolate your 802.11n traffic from your 802.11b/g traffic on the 2.4GHz radio. This will prevent slowdown that can occur when legacy clients coexist with 802.11n clients.

So yes, you're correct to say that it does work better in 5GHz. The nice thing is that most 802.11n chips in laptops support this band.

That said, it would be best if voice and data can both exist in the 5GHz space. You can accomplish this by creating different SSIDs for your voice and data networks. There is nothing wrong with deploying both in 5GHz.

Let me know if you have anymore questions. Thanks!

Jeff

scott.stapleton Wed, 04/22/2009 - 04:46

As far I know, bonding is supported in 2.4Ghz. Sure, there *can* be issues, but you are saying this does not work at all.

A little under 150 Mbps should be able to be achieved at 2.4Ghz without channel bonding, in a good environment (granted, there are fewer and fewer around).

jeff.kish Wed, 04/22/2009 - 05:27

Well, I said it's limiting, not that it doesn't work. And I'm sorry, I was referring to 150Mbps of throughout, not absolute data rates. You can hit 300Mbps absolute with channel-bonding, which provides around 150Mbps actual throughput.

gamccall Wed, 04/22/2009 - 05:51

Although it is an optional part of the 11n standard, Cisco does not support bonding in 2.4GHz.

George Stefanick Sat, 04/25/2009 - 09:35

In years past we didnt have option of 802.11a on VoIP. VoIP was only on b for a very long time and then g and now recently a.

I am seeing a big move in Healthcare to move VoIP to a and data to g. The 2.4GHz spectrum is so much like the "wild west". You have so many devices that occupy this space today not to mention all the contention of other 802.11 devices all "fighting" for access to the medium.

Im excited to have 802.11n as the next step. Although i dont think nor have i heard of any manufactures committing to a 802.11n phone "yet".

I also say, if you design it right and manage your WLAN (clints/ RF / Config) you can have a stellar 2.4GHz network with VoIP and DATA.

Me personally, VoIP lives on A data lives on G ... N lives on 5 GHz.

scott.stapleton Tue, 04/28/2009 - 20:59

This seems like a software limitation which I would hope Cisco will address in the future. There are times when bonded channels at 2.4 Ghz would certainly make sense without causing problems.

Dominic Stalder Sun, 05/03/2009 - 22:52

And what channels would you use, if we want to activate the 802.11n in 5 GHz with Channel Bonding (40 MHz)?

dennischolmes Mon, 06/08/2009 - 07:37

Guys,

This is not a question of software or controller code. 2.4 available spectrum in the US eliminates the ability to efectively run channel bonding in the 2.4 space. Why? You only have 2 nonoverlapping channels. With 5ghz you in theory have 11-12 good channels to choose from. It is a spectrum issue.

scott.stapleton Mon, 06/08/2009 - 17:45

Whilst this is the case, there are environments where 1 x bonded channel and 1 x non-bonded channel would work fine. I feel the decision should be left up to the implementor, based on his or her particular environment.

When I last checked the draft standard, bonding was allowed at 2.4 Ghz with it being optional?

jeff.kish Tue, 06/09/2009 - 05:07

Right now it's allowed, but it's not required as part of the standard. That's why Cisco can get away with not including it.

The problem is that bonding in the 2.4GHz space doesn't play friendly with anyone else. If one person in an apartment complex uses a bonded 2.4GHz channel, he just doubled his interference profile. And even in a corporate environment, there are going to be very rare cases where you'd want a mixed environment of bonded and non-bonded channels. It's almost impossible to do it that way.

I've heard that the final standard might ban bonded 2.4GHz channels. Apparently that's still something that's undecided. With that in mind, maybe Cisco's ahead of the game.

bailey.jeff Mon, 06/22/2009 - 11:00

You also cant use channel bonding in the 5 GHz spectrum if you plan on using Voice services in that band. Cisco documentation states this.

Matthew Fowler Mon, 06/22/2009 - 16:46

Just to clear things up here, channel bonding IS supported in 2.4GHz by Cisco (but not recommended).

The confusion may be because 40MHz RRM in 2.4GHz is not supported. So, you can statically set it to 40MHz, but can only run RRM with 20MHz channels. This makes sense because RRM would be too limited in what channels it could assign.

scott.stapleton Fri, 06/26/2009 - 01:11

Thanks for clearing that up Matt. As mentioned, I feel Cisco should support bonding at 2.4 Ghz and leave it up to the skill of the implementor to decide when to use it and when not to. If most cases I would not however we do have clients literally in the middle of nowhere where I would like the ability to utilise bonding at 2.4 Ghz if I deem appropriate.

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